Add local_generic rootfs-images repository

Declares a local generic (raw-file) repo for bootapi's node rootfs tarballs and
wires the local_generic kind through the module. Depends on
terraform-provider-artifactapi #12 releasing v0.1.4 (adds artifactapi_local_generic);
the provider version pin is bumped to 0.1.4, so plan/validate stay red until that
release is available.

- config/local_generic/rootfs-images.yaml (new repo).
- local_generic wiring: config.hcl, module variables.tf + main.tf, env
  terragrunt.hcl inputs; provider pin 0.1.3 -> 0.1.4.

Claude-Session: https://claude.ai/code/session_015ur3i7D2azsMAWTSVABApv

modules/artifactapi/variables.tf

@@ -112,6 +112,14 @@ variable "local_rpm" {
   default = {}
 }
 
+variable "local_generic" {
+  description = "Map of local generic (raw-file) repositories"
+  type = map(object({
+    description = optional(string, "")
+  }))
+  default = {}
+}
+
 variable "local_terraform" {
   description = "Map of local Terraform repositories"
   type = map(object({